Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2002-01-18
2003-11-25
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
Reexamination Certificate
active
06652041
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a hydraulic pressure control device for a vehicle, particularly one including an electronic control device to compute optimum braking conditions based on information from various sensors to make possible various controls such as applying brakes even while the driver is not operating brakes, generating braking force larger than the amount the driver is operating to produce, or lowering the braking force even though the driver has no intension of relaxing the brakes, with a simple structure. This invention also relates to a vehicle brake system using it.
A so-called brake-by-wire type vehicle brake system has been developed in which in order to electrically control braking forces applied to the vehicle, the amount of braking applied by the driver and the hydraulic pressure generated by the brake operation are converted to electric signals and the hydraulic pressure generated in the power line (that is, pressure source including a power-driven pump) is adjusted to a value corresponding to the electric signals and supplied to the wheel brakes.
Also, in a general one of brake systems of this kind, if a solenoid valve in the passage connecting the power line with the wheel brakes should not open due to failure of electric line, even if pressure is accumulated in the power line, it becomes impossible to effectively use it for braking. Thus, the present inventors have developed a brake system as shown in FIG.
10
.
In the device of
FIG. 10
, a proportional pressure control valve
60
is provided in a passage
49
extending from a pressure source
50
provided with pumps
46
driven by a motor
45
, a pressure accumulator
47
and a hydraulic pressure sensor
48
to the wheel brakes
38
(added symbols specify the respective wheels, namely FR shows front right wheel; FL, front left wheel; RR, rear right; and RL, rear left). When the brake pedal
31
is depressed, a passage
34
extending from a master cylinder
32
to the wheel brakes
38
is shut off with a solenoid valve
35
, the amount of applying the brake pedal
31
and the hydraulic pressure generated in the master cylinder
32
are detected by a stroke sensor
44
and a hydraulic pressure sensor
39
, respectively, and converted to electric signals in an electronic control device
40
, and a current corresponding to the electric signals is supplied to the proportional pressure control valve
60
to adjust the hydraulic pressure for the wheel brakes
38
to a value corresponding to the brake operating amount with the proportional pressure control valve
60
.
In the proportional pressure control valve
60
, as shown in
FIG. 11
, a spool valve
62
is inserted in a housing
61
having an input port
61
a,
output port
61
b
and discharge port
61
c.
The spool valve
62
is driven by a magnetic force generated by activating a coil
66
a
of a solenoid
66
to selectively connect the output port
61
b
to the input port
61
a
or the discharge port
61
c
and adjust the degrees of opening of passages formed between a shoulder portion on the outer periphery of the spool valve
62
and edge portions of the respective ports. The spool valve
62
has opposed pressure-bearing surfaces having a difference in area which is equal to the sectional area of a pin
65
inserted into a pin hole
64
. Thus, assuming that the hydraulic pressure P introduced through the input port
61
a
is P, the force of a return spring
63
is F, the current supplied to the coil
66
a
is I, and the sectional area of the pin
65
is S, the thrust force acting against the spool valve
62
balances at the position where the following formula is met:
P·S+F=aI
2
(a is a constant)
and the spool valve
62
stops at this position.
Replacing the above formula,
P
=(
a·I
2
−F
)/
S
In this formula, a and S are constants. If the spring constant is ignored, F can also be regarded as a constant. Thus, the hydraulic pressure P is proportional to the square of the current I and depends on the amount of applying the brake pedal
31
.
In the system of
FIG. 10
, if the electromagnetic force is not produced in the proportional pressure control valve
60
due to failure of the electric line, a solenoid valve
43
in a passage
42
opens, so that the hydraulic pressure generated in the master cylinder
32
acts on the proportional pressure control valve
60
. By the hydraulic pressure, an auxiliary piston
67
in
FIG. 11
is pushed and the movement of the auxiliary piston
67
is transmitted to the spool valve
62
to adjust the position of the spool valve. Thus, the hydraulic pressure in the pressure source
50
is adjusted by the proportional pressure control valve
60
, supplied to boost pistons
36
of
FIG. 10
, and the hydraulic pressure generated by the boost pistons
36
is supplied to the wheel brakes
38
. Thus, even if the proportional pressure control valve
60
cannot be driven with a magnetic force, it is possible to apply the brakes by effectively using the hydraulic pressure in the pressure source
50
.
Among brake systems developed by the present inventors, there is one in which during failure of the electric line or if the amount of applying the brake pedal exceeds a predetermined amount, the proportional pressure control valve (spool valve) is driven by the brake pedal force.
JP patent publication 2000-326839 also discloses a system in which during failure of the electric line, the spool valve is driven by the brake pedal force.
The brake system of
FIG. 10
, which was developed by the present inventors, needs a master cylinder and a plurality of solenoid valves. It also needs a stroke simulator
52
of
FIG. 10
for taking in brake fluid fed from the master cylinder while the system is operating normally, and a solenoid valve
51
that closes the inlet side passage of the simulator during failure of the electric line. This incurs complicatedness of the structure and cost increase.
With the earlier developed system in which the spool of the proportional pressure control valve can be moved by the brake pedal in an emergency, since the spool is driven by the brake pedal only in an emergency in which the spool cannot be driven with an electromagnetic force or if the amount of applying the brake pedal exceeds a predetermined amount, electronic control is indispensable during normal braking. For one in which the spool is driven by the brake pedal in an emergency, a clutch for separating the spool valve from the brake pedal in a normal state is needed. On the other hand, one in which the spool is driven by the brake pedal after the amount of applying the brake pedal has exceeded a predetermined amount has a problem that responsiveness lowers in an emergency.
The system disclosed in JP publication 2000-326839 is also provided with a mechanism for preventing the movement of the brake pedal from being transmitted to the spool valve in a normal state. This complicates the structure. Also, with this system, since a hydraulic pressure generating device for adjusting pressure is provided independently of the brake pedal and the brake pedal force is transmitted to a lever in the hydraulic pressure generating device through a wire, the layout of the instruments is also complicated.
Thus, in view of reliability and cost, it is required to reduce elements that can cause a failure and cost increase and to improve responsiveness not only in a normal state but in an emergency.
On the other hand, if one tries to perform various kinds of controls, it is necessary that both control based on the intension of the driver and control by judgment of the electronic control device, separate from the intension of the driver, can be performed.
An object of this invention is to answer these requirements with a system that employs a proportional pressure control valve and is simple in structure.
SUMMARY OF THE INVENTION
According to this invention, there is provided a hydraulic pressure control device for a vehicle comprising a housing formed with an input port, an output port and a discharge port, a proportion
Nakano Keita
Nishikimi Makoto
Yoshino Masato
Advics Co., Ltd.
Burns Doane , Swecker, Mathis LLP
Schwartz Christopher P.
LandOfFree
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